This invention relates to well drilling apparatus and more particularly to an improved rotating drilling head. The drilling apparatus generally comprises a rotatable drill stem used to rotate a drill bit within the well. The drill stem may include a string of drill pipes connected with a non-circular cross-section pipe, commonly referred to as a kelly, slidably extending downwardly through the rotary table. The kelly, being a part of the drill stem, transmits the drive from the rotary table to the drilling head via the kelly bushings. In the usual forward circulation drilling operation, a drilling fluid such as a liquid or compressed air or gas may be forced through the interior of the hollow drill stem and drill bit at the bottom of the well bore. Cuttings and debris at the bottom of the well are entrained in the drilling fluid and carried upwardly in the annulus between the outside of the drill stem and the inside surface of the well bore or casing. In a reverse circulation drilling operation, the drilling fluid is pumped down the annulus between the well bore or casing and forced upward through the drill bit and interior of the hollow drill stem.
The rotating drilling head is attached to the top of a well stack which may have a conventional blowout preventer at its upper end.
The drilling head includes a stationary outer housing or tubular spool which is secured to the top of the stack, a drive ring and bearing assembly, and a drive assembly which is matable with the drive ring and bearing assembly. The drive assembly includes a split kelly bushing. A rubber stripper is attached for rotation with the drive ring in slidable sealing engagement with the kelly drive.
In operation, the split kelly bushing is slidably connected to the kelly drive. As the kelly drive is lowered through the drilling head the kelly bushing is received within the drive assembly. Rotation of the kelly causes the kelly bushing to rotate which rotates the drive assembly, which in turn rotates the drive ring and attached rubber stripper. Thus, in operation, there is no relative rotational movement between the rubber stripper and the kelly drive.
Various arrangements have been provided for removing worn drilling head components from the spool. In certain arrangements, an expandable/contractible split clamp is employed to removably secure such drilling head components to the spool. Such clamps incorporate a plurality of pivoting segments which together may be moved radially outward or inward by a remote controlled hydraulic motor driven screw. Such remote control eliminates the need for a workman to go under the rig floor and manually operate the clamp. Problems have been experienced with such split clamps. For example, mud and debris tend to accumulate about the clamp segments which obstructs proper radial movement. Also, it is necessary to connect/disconnect a lubrication line directly to the spool at a location relatively remote from the bearing assembly.
An object of the invention is to facilitate the assembly, installation, operation and maintenance of a drilling head in which components subject to wear may be readily removed for replacement and reinstalled.
Another object of the invention is to releasably secure removable components to the drilling head spool with a reliable clamp which operates properly in the presence of mud and debris which tends to obstruct the remote controlled operation of multi-segmented clamps.
Still another object of the present invention is to facilitate lubrication of the rotating components, seals and the bearing assembly of the drilling head.
The above objects and many other objects, features and advantages of the present invention will become apparent to those skilled in the art when the detailed description of the preferred embodiment is read in conjunction with the drawings.